Methods of manufacturing wire, multi-layer wire pre-products and wires

ABSTRACT

Exemplary methods for manufacturing a wire and resultant wires are disclosed herein. The method includes extruding a receptor cross-linkable polymer that is substantially free of curing agent about a conductive core and extruding a donor polymer in association with a curing agent. The method includes disposing the donor polymer about the receptor polymer and conductive core to create a multi-layer wire pre-product. The method also includes heat curing a multi-layer wire pre-product to form a wire.

This application is a divisional of U.S. patent application Ser. No.13/085,253, filed Apr. 12, 2011, which is incorporated herein byreference.

TECHNICAL FIELD

The present disclosure refers to exemplary methods for manufacturingwires, as well as to exemplary multi-layer wire pre-products andexemplary wires.

BACKGROUND

The term “wire” as used herein refers to a conductive core, wherein theconductive core is enveloped by at least one insulative layer. The term“wire” as used herein also encompasses cables, or groups of two or moreinsulated conductive cores.

Wires have been ubiquitous since at least the Industrial Age for alltypes of electrical applications. These applications include, withoutlimitation, commercial and residential power supply, appliances,computers and personal electronics of all shapes and sizes, vehicles ofall types, including fossil fuel-powered and electrically-poweredautomobiles and recreational vehicles.

Historically, wires were manufactured by a simple heat-curing method.The historical heat-curing method involved feeding a conductive coreinto an extruder wherein at least one insulative layer was extrudedabout the conductive core. To form insulative layers using such methods,all starting materials, including cross-linkable polymers and theirassociated curing agents, were combined in an extruder prior toextrusion. Then, the starting materials were extruded about theconductive core at temperatures ranging from about 80° C. to about 110°C. depending upon the particular materials. Next, the extruded wirepre-product was heat cured at temperatures ranging from about 135° C. toabout 155° C. for a length of time to cause sufficient cross-linking inthe insulative layer or layers to confer onto the insulative layer orlayers the desired properties, including physical, mechanical and/orelectrical properties.

Such historical heat-curing methods were efficient and relativelyinexpensive. For example, by adding all of the starting materials to theextruder at roughly the same time, manufacturers may have realized again in manufacturing efficiency. That is, manufacturers could avoidslowing manufacturing line speeds and could avoid purchasing additionalequipment to manage the addition of separate materials at separatetimes.

However, historical heat-curing methods faced numerous challenges. Forexample, manufacturers sought to avoid premature cross-linking duringextrusion, also known as scorching. Significant scorching could damageextrusion equipment and generate wire that would not meet technicalspecifications, including physical, mechanical and/or electricalspecifications. Accordingly, manufacturers were left to experiment withpolymer and curing agent combinations to minimize scorching.

Eventually, technical demands on wire became more sophisticated, andwire produced by historical heat-curing methods failed to satisfy avariety of technical specifications. This occurred in many industries.By way of non-limiting example, in the automotive industry, certainoriginal equipment manufacturers (OEMs) require wire to withstand scrapeabrasion such that when a conductive core of a wire has across-sectional area of 0.22 mm² or less, the insulation on the wireremains intact following 150 cycles of abrasion scrapes with a needlehaving a diameter of 0.45±0.01 mm. Wire manufactured by historicalheat-curing methods does not satisfy this standard.

To meet the growing technical demands on wire, manufacturersincreasingly turned away from historical heat-curing methods and towardradiation or electron beam (e-beam) manufacturing methods. Indeed,e-beam manufacturing methods remain in use today.

E-beam manufacturing methods typically involve feeding a conductive coreinto an extruder where at least one insulative layer is extruded aboutthe conductive core. To form an insulative layer, all starting materialsfor the layer are added to the extruder. Then, the starting materialsare extruded about the conductive core. Next, the extruded wirepre-product is collected on a spool before being exposed to radiation.Radiation initiates curing, so curing agents are not typically used ine-beam manufacturing methods.

E-beam manufacturing methods have advantages over historical heat-curingmethods. As non-limiting examples, the cross-linking reaction in e-beammanufacturing methods is faster and more uniform, especially for thinwall wires. The e-beam manufacturing methods produce wire that satisfiesmore challenging technical specifications. As a non-limiting example,e-beam manufacturing methods are more effective at preparingabrasion-resistant wires and ultra thin wall wires with a temperatureclass rating of Class D (150° C.) or higher.

E-beam manufacturing methods, however, also involve numerous challenges.The equipment is expensive and there are attendant safety procedures andprecautions whenever radiation is used in a manufacturing method. Thesesafety efforts can add to expenses and slow manufacturing line speeds.Additionally, e-beam manufacturing methods may be more difficult to usewith thick wall wires. This may be because, at commercially acceptablemanufacturing line speeds, there is a potential for incompletepenetration of electron beams through a dense polymeric insulative layeror layers. Incomplete penetration can lead to incomplete curing, whichin turn can cause wire to fail technical specifications. For example,the insulation of the wires may swell or crack.

Additionally, using e-beam manufacturing methods to form very flexiblewire presents challenges. This may be because, to spool extruded wirethat is not yet cured (that is, extruded wire pre-product), theinsulative layer or layers must be sufficiently hard to avoid becomingmisshapen or deformed. Generally, this requires the extruded wirepre-product to have a hardness of about 80 Shore A or higher. Aftercuring, the cross-linked polymer in the wire causes the wire to besubstantially harder than the extruded wire pre-product. As a result,wire made by e-beam manufacturing methods can fail to achieveflexibility-related mechanical properties desired for certain industrialapplications. By way of non-limiting example, it may be useful toproduce a flexible wire having a tensile stress at yield of less than 9MPa and a tensile modulus at 200 MPa. Wire produced by e-beammanufacturing methods would not be expected to exhibit such mechanicalproperties.

Accordingly, there is a need for improved manufacturing methods andwires. Efficient and cost effective methods are desired that can producewires that meet can meet increasingly demanding technicalspecifications.

BRIEF DESCRIPTION OF THE DRAWINGS

While the claims are not limited to the illustrated examples, anappreciation of various aspects is best gained through a discussion ofvarious examples thereof. Referring now to the drawings, illustrativeexamples are shown in detail. Although the drawings represent theexemplary illustrations, the drawings are not necessarily to scale andcertain features may be exaggerated to better illustrate and explain aninnovative aspect of an embodiment. Further, the specific examplesdescribed herein are not intended to be exhaustive or otherwise limitingor restricting to the precise form and configuration shown in thedrawings and disclosed in the following detailed description. Exemplaryillustrations are described in detail by referring to the drawings, asfollows:

FIG. 1 illustrates an exemplary method of manufacturing wire.

FIG. 2 illustrates an exemplary method of manufacturing wire.

FIG. 3 shows a cross-section of an exemplary multi-layer wirepre-product.

FIG. 4 shows a cross-section of an exemplary multi-layer wirepre-product.

FIG. 5 graphically depicts cure completion testing results of exemplarywire.

FIG. 6 graphically depicts scrape abrasion testing results of exemplarywire.

FIG. 7 graphically depicts scrape abrasion testing results of exemplarywire.

DETAILED DESCRIPTION

Reference in the specification to “an exemplary illustration”, an“example” or similar language means that a particular feature,structure, or characteristic described in connection with the exemplaryapproach is included in at least one illustration. The appearances ofthe phrase “in an illustration” or similar type language in variousplaces in the specification are not necessarily all referring to thesame illustration or example.

Referring to FIGS. 1 and 3, an exemplary process for manufacturing wiresis depicted, as is an exemplary multi-layer wire pre-product 25.Generally, a conductive core 15 is fed into an extruder 20. Monomers,oligomers or polymers to form a cross-linkable receptor polymer 22 areadded to a hopper of the extruder 20. No curing agent is added.Separately, monomers, oligomers or polymers to form a donor polymer 23are added to a different hopper of the extruder 20. Curing agent to beassociated with the donor polymer 23 is included in the hopper with thedonor polymer 23 and any other starting materials. The receptor polymer22 is then co-extruded with the donor polymer 23, the donor polymer 23being associated with a curing agent. A multi-layer wire pre-product 25is generated from the co-extrusion process. The multi-layer wirepre-product 25 includes the donor polymer 23 disposed about the receptorpolymer 22, which is in turn disposed about the conductive core 15. Theterm “about” as used herein means circumferentially enveloping, but notnecessarily in direct contact. The multi-layer wire pre-product 25 isheat cured at heat curing station 35 to generate resultant wire 40.Unexpectedly, the resultant wire 40 has properties thought to beachievable only through e-beam manufacturing methods.

The exemplary process depicted in FIG. 1 is not generally limited by thematerials selected for use as conductive cores 15. Also, except for melttemperatures, the exemplary process is similarly not limited by theparticular cross-linking polymer selected for use as a receptor polymer22 or by the polymer selected for use as a donor polymer 23.

Conductive Cores

“Conductive core”, as used herein, refers to at least one material suchas a metal or a metalloid having conductive or semi-conductiveproperties for use in a wire. A wide range of conductive cores 15 may besuitable for use with the methods and wires disclosed herein. That is,the conductive core 15 may have a range of chemical compositions, solong as the conductive core 15 conducts electricity sufficiently for theapplication. Suitable conductive cores 15, for example, may include ametal comprising at least one of copper, nickel silver, beryllium,phosphor bronze, nickel, aluminum, or steel. Additionally, metals may beplated with another metal-containing material. For example, tin-plating,silver-plating, gold-plating, or nickel-plating may be suitable for usewith the methods and wires disclosed herein. Exemplary conductivematerials may also include copper-clad aluminum and copper-clad steel.

In applications where the conductive core 15 is semi-conductive,conductive core 15 may include a range of suitable semi-conductivematerials. Such materials may include, with out limitation, silicon,graphite, germanium, antimony and gallium arsenide phosphide.

Conductive cores 15 may be configured in any of a wide range ofarrangements. For example, the conductive core 15 may be solid (i.e.,comprise a single strand of metal), or the conductive core 15 may bestranded. When the conductive core 15 is stranded, any number of strandsmay be used. For example, the number of strands can equal or exceed 6,19, 37, 50, 154, 494, 741 or 1140 strands. The strands may all be of thesame chemical composition, or different strands may have differentchemical compositions. A wide range of configurations of strands may besuitable for the use with the methods and wires disclosed herein. Forexample, the strands say be woven or non-woven. Additionally, theconductive core 15 may comprise layers of strands upon one another. Theconfiguration of adjacent layers of strands can be the same as ordifferent from one another, whether woven or non-woven.

The conductive core 15 may have a cross-sectional area of a wide rangeof sizes. For example, cross-sectional areas of conductive core 15 maybe as small as about 0.13, 0.22, or 0.35 mm². Additionally,cross-sectional areas of conductive core 15 may be as large as or largerthan about 1, 2, 3, 4, 5 or 6 mm².

The conductive core 15 may have any set of properties desired for aparticular application. For example, with respect to electricalproperties, the conductive resistance of a conductive core 15 can be aslow as about 0.1 mOhm/m at 20° C. or as high as about 130 mOhm/m at 20°C. In other words, properties such as electrical properties ofconductive cores 15 do not limit the methods and wires disclosed herein.

Cross-Linkable Receptor Polymers

“Cross-linkable receptor polymers”, as used herein, refers to polymershaving a chemical structure such that the polymers are capable ofcross-linking upon curing, the receptor polymers being substantiallyfree of curing agent. “Substantially free”, as used herein, encompassesthe complete absence of curing agents, but also allows for incidentaland/or trace amounts of curing agents to be detectable in the receptorpolymer 22 using standard chemical analytical methods. Such incidentaland/or trace amounts of curing agents should not comprise more thanabout 0.2% or more than about 1% by weight of the receptor polymer.

A wide range of cross-linkable polymers or cross-linkable polymercombinations may be suitable for use as a receptor polymer 22 so long asthe receptor polymer 22 has a melt temperature higher than an extrusiontemperature and higher than a melt temperature for a donor polymer 23.“Melt temperature”, as used herein, refers to the temperature range whena polymer transitions from a crystalline or semi-crystalline phase to aviscous amorphous phase. “Extrusion temperature”, as used herein, refersto the temperature at which resins in the extruder 20 exit the extruder20 through a nozzle.

The difference in melt temperature between the receptor polymer 22 andthe donor polymer 23 should be large enough to avoid scorching and smallenough to generate a sufficient state of cure to confer desiredproperties upon the insulation of wire 40. The difference in melttemperature between the receptor polymer 22 and the donor polymer 23 maybe at least about 5° C., at least about 10° C. at least about 20° C., orleast about 40° C. The difference in melt temperature between thereceptor polymer 22 and the donor polymer 23 may be greater or lower,depending upon the materials used for the receptor polymer 22 and thedonor polymer 23 and the intended use of the wire 40.

To avoid scorching, melt temperatures for suitable receptor polymers 22should be higher than the extrusion temperature. Exemplary melttemperatures for suitable receptor polymers 22 may be, on the low end,as low as or lower than about 125° C., about 135° C. or about 150° C.Exemplary melt temperatures for suitable receptor polymers 22 on thehigh end may be as high as or higher than about 200° C., about 250° C.or about 300° C. The range of suitable melt temperatures for receptorpolymers 22 may vary depending upon the materials used for the receptorpolymer 22 and the donor polymer 23 and the intended use of the wire 40.

Suitable cross-linkable receptor polymers 22 may include one or more ofsubstituted or unsubstituted cross-linkable polyolefins such aspolyethylene (including by way of non-limiting example, one or more ofultra high molecular weight polyethylene (UHMWPE) or high densitypolyethylene (HDPE)). Additional suitable receptor polymers 22 mayinclude polyvinyl chloride (PVC), ethylene vinyl acetate (EVA) andcross-linking fluoropolymers. Suitable commercially available receptorpolymers 22 may include PETROTHENE® HDPE from Lyondell, MARLEX® HDPEfrom Chevron Phillips Chemical Co., TEFLON® and TEFZEL® fluoropolymersfrom Dupont, or KYNAR® and KYNAR FLEX® fluoropolymers from Arkema.

Donor Polymers

“Donor Polymers”, as used herein, refers to polymers having curing agentassociated therewith to eventually migrate from the donor polymer 23 tothe receptor polymer 22. A wide range of polymer or polymer combinationsmay be suitable for use as a donor polymer 23 so long as the donorpolymer 23 has a melt temperature lower than the receptor polymer 22, asdescribed above. Additionally, the donor polymer 23 may have a melttemperature at or below the extrusion temperature. To avoid prematuremigration of curing agent and scorching, melt temperatures for suitabledonor polymers 22 should not be too far below the extrusion temperature.Exemplary melt temperatures for suitable donor polymers 23 may be, onthe low end, as low as or lower than about 55° C., about 70° C. or about80° C. Exemplary melt temperatures for suitable donor polymers 23 on thehigh end may be as high as or higher than about 100° C., about 115° C.or about 125° C. The range of suitable melt temperatures may varydepending upon the materials used for the receptor polymer 22 and thedonor polymer 23 and the intended use of the wire 40.

Donor polymers 23 may be cross-linkable, but need not be cross-linkable.Suitable donor polymers 23 may include one or more of substituted orunsubstituted cross-linkable polyolefins such as polyethylene (includingby way of non-limiting example, one or more of linear low-densitypolyethylene (LLDPE) or low-density polyethylene (LDPE)). Suitable donorpolymers may also include ethylene-propylene copolymers (EPM),ethylene-propylene-diene (EPDM) elastomers, ethylene vinyl acetate (EVA)or ethylene-vinyl acetate copolymer (EVM). Suitable commerciallyavailable donor polymers 23 may include ELVAX® EVA from Dupont,LEVAPRENE® EVM from LANXESS, PETROTHENE® LDPE from Lyondell, BOREALIS®LDPE from Borealis AG, ROYALENE® EPDM from Lion Copolymer, NEOPRENE®synthetic rubber from Dupont, NORDEL IP® hydrocarbon rubber from The DowChemical Co., ENGAGE® polyolefin from The Dow Chemical Co., TAFMER®alpha-olefin copolymer from Mitsui Chemical, and TYRIN® chlorinatedpolyethylene resin from The Dow Chemical Co.

Donor polymers 23 must be associated with at least one curing agent. Awide range of curing agents may be used. For example, curing agents mayinclude one or more peroxides. Exemplary peroxides may include diacylperoxide, dalkyl peroxide, hydroperoxides, ketone peroxide, organicperoxide, peroxy(di)carbonate, peroxyester, and peroxyketal. Curingagents may also include, sulfur, amines, and diamines, or anycombination thereof. Suitable commercially available curing agents mayinclude DI-CUP®, LUPEROX LP®, LUPEROX 101®, LUPEROX 224®, VUL-CUP R® andVUL-CUP 40KE® peroxides from Arkema, VAROX DCP®, VAROX VC-R®, VAROX DBPHperoxides from Vanderbilt Co. Inc.

Coagents may optionally be included with one or more curing agents. Arange of coagent may be used. Coagents may include, for example, one ormore of di- or tri-functional acrylate or methacrylate, vinyl butadiene,vinyl butadiene-styrene copolymers. Coagents may optionally be includedwith the starting materials for the receptor polymer 22 or the donorpolymer 23 or both.

The amount of curing agent associated with the donor polymer 23 shouldbe enough so that sufficient curing agent migrates from the donorpolymer 23 to the receptor polymer 22 during heat curing to causesufficient cross-linking to confer the desired properties onto wire 40.Too little curing agent may lead to insufficient cross-linking, therebygenerating wires that fail to satisfy technical specifications.Exemplary problems associated with insufficient curing or cross-linkingmay include swelling or cracking of wire insulation during manufactureor use.

By way of non-limiting example, for wires to be used in the automotiveindustry, too little curing agent may cause a wire 40 to fail one ormore of the tests set forth in International Organization forStandardization (ISO) 6722 for road vehicles 60V and 600V single-corecables, which is incorporated by reference herein in its entirety. Amongother tests, the ISO standards delineate a pressure test at hightemperature, abrasion tests, heat aging tests, and tests for resistanceto chemicals.

For the pressure test described in Section 7.1 of ISO 6722, wire samplesare subjected to a load that is calculated as a function of thecross-sectional area of the conductive core of the wire (the outsidediameter of the wire less the nominal thickness of the insulation in thewire), and heated for 4 hours in an oven. The temperature of the ovendepends on the class of the wire being tested. For example, Class Arated wire would be heated to 85±2° C., whereas Class B rated wire wouldbe heated to 100±2° C. The wire samples are then immersed in a saltwater bath for 10 seconds, then subjected to 1 kV for 1 minute. Ifbreakdown of the wire samples does not occur, then the wire samples passthe test.

There are two exemplary resistance-to-abrasion tests delineated in ISO6722, a needle test (Section 9.3) and a sandpaper test (Section 9.2).For the needle test, a needle having a diameter of about 0.45± 0.01 mmmay be selected to make abrasions of about 15.5±0.1 mm in length at afrequency of about 55±5 cycles per minute. An applied force of 7 N±0.mm²is exerted upon the sample wires. Suppliers and OEMs supplement the ISOstandard by agreeing how many cycles of abrasion scrapes a wire having aconductive core of a particular cross-sectional area must endure whilethe insulation of the wire remains intact. For example, OEMs may requirea supplier to manufacture a wire having a conductive core with across-sectional area of 1.5 mm² or greater, and require that theinsulation of such a wire remain intact following at least 1500 cyclesof abrasions. Similarly, OEMs may require a supplier to manufacture awire having a conductive core with a cross-sectional area of about 0.22mm² or less, and require that the insulation of such a wire remainintact following at least 150 cycles of abrasion scrapes. Otherspecifications are contemplated, such as wires having a conductive corewith a cross-sectional area of about 0.35 mm² or about 0.5 mm², whichare common wire sizes. For such wires, technical specifications mayrequire insulation to withstand at least 200 or 300 cycles of abrasionscrapes, respectively.

For the ISO 6722 sandpaper test, 150 J garnet sandpaper is applied tosample wires at a rate of 100±75 mm/min with an applied force of atleast 0.63 N. Depending upon the cross-sectional area of the conductivecore, an additional mass of a pre-selected magniuude is added to theapparatus to apply additional force on the sample wires. The sandpaperis drawn across the wire until at least some of the conductive core isexposed. The length of the sandpaper required to expose the conductivecore is recorded as the measure of resistance to sandpaper abrasion. TheISO 6722 standard increases the length of sandpaper required to pass thetest with the cross-sectional area of the conductive core of the samplewires. For example, a 60V thin wall wire for smaller gauge wires wouldrequire testing with an additional mass of 100 g, and the length of thesandpaper making the abrasion on the sample wire without exposing theconductive core would be 200 mm in length for a conductive core having across-sectional area of 0.13 mm², 224 mm in length for a conductive corehaving a cross-sectional area of 0.22 mm², and 250 mm in length for aconductive core having a cross-sectional area of 0.35 mm². Bycomparison, a 60V thin wall wire for larger gauge wires would requiretesting with an additional mass of 200 g, and the length of sandpapermaking the abrasion on the sample wire without exposing the conductivecore would be 300 mm in length for a conductive core having across-sectional area of 0.5 mm², 450 mm in length for a conductive corehaving a cross-sectional area of 1.5 mm², and 500 mm in length for aconductive core having a cross-sectional area of 2.0 mm².

Heat aging tests are described in Section 10 of ISO 6722. For example,for long term aging, sample wires are placed in an oven for 3000 hours.The temperature depends upon the class rating of the sample wires. Forexample, class C wire is heated at 125±2° C. and class D wire is heatedat 150±2° C. This simulates aging. After simulated aging, the samplewires are cooled at room temperature for at least about 16 hours, thenthe wires are wound into a winding. If any of the conductive core isexposed in the winding (that is, if the insulation cracks), then thesample wire fails the test. If not, the sample wire is immersed in asalt water bath for 10 minutes, then subjected to 1 kV for 1 minute. Ifbreakdown of the sample wires does not occur, then the sample wires passthe test.

Resistance-to-chemicals tests are described in Section 11 of ISO 6722.For example, for resistance to hot water, closely wound sample wires ofa specified length are immersed in a salt water bath at 185±5° C. for 7days, which completes one cycle. After five cycles, the sample wires arecooled, visually inspected, then subjected to 1 kV for 1 minute. Ifthere is no cracking on the insulation, the sample wires pass the visualinspection. If breakdown of the sample wires does not occur, then thesample wires pass the test.

Unexpectedly, wires 40 manufactured by the methods disclosed hereinpassed the battery of tests disclosed in ISO 6722 with cross-linkedinsulation of the wires 40 having a state of cure as low as 50%.Generally, to pass a battery of tests such as those described above anddetailed in ISO 6722, sufficient curing agent should be associated withthe donor polymer 23 to ensure a state of cure of at least about 50% ofthe receptor polymer 22 collectively with any and all other insulativecross-linkable polymers in the wire 40. There may be instances wheretechnical specifications can be satisfied with an even lower state ofcure. Additionally, there may be instances where a state of cure of atleast about 75% is desired to satisfy particular technicalspecifications. On the low end, curing agents may comprise about 0.25%by weight of the polymer or polymers comprising the receptor polymer 22together with any other cross-linkable polymers in the wire 40, butweigh percentages may be about 0.5%, about 1.0%, 2.0% or about 3.5% ofthe total cross-linkable starting materials. Depending upon theparticular application for the wire 40 and technical specificationsplaced upon the wire 40 to be manufactured, less or more curing agentmay be added than the specific ranges exemplified herein.

Optional Materials

Except for the issues specific to curing agents as described herein, awide range of additional ingredients may be placed in the extruder 20 tobe extruded with the receptor polymer 22 or the donor polymer 23. Suchingredients may include, by way of non-limiting example, monomers,oligomers or polymers to form one or more thermoplastic polymerinsulative layers, fire retardants, processing aids, antioxidants,thermal stabilizers, elastomers, reinforcing fillers, antiozonants,accelerants, vulcanization agents, crack inhibitors, metal oxides andpigments.

Multi-Layer Wire Pre-Product

In multi-layer wire pre-product 25, receptor polymers 22 and donorpolymers 23 may be disposed in any layer configuration so long as thereceptor polymer 22 is between the conductive core 15 and the donorpolymer 23. The receptor polymer 22 and the donor polymer 23 need not bein direct contact with one another or with the conductive core 15.

Referring to FIGS. 3 and 4, exemplary configurations of insulativelayers comprising receptor polymers 22 and donor polymers 23 aredepicted. In FIG. 3, an exemplary multi-layer pre-product 25 is shown.Receptor polymer 22 is in direct contact with conductive core 15, anddonor polymer 23 is in direct contact with the receptor polymer 22. InFIG. 4, an exemplary multi-layer pre-product 25′ is shown. Insulativelayer 26 is disposed between the conductive core 15 and the receptorpolymer 22, and insulative layer 27 is disposed between the receptorpolymer 22 and the donor polymer 23. Insulative layers 26 and 27 may bethe same or different, and may comprise any of a wide range of polymeror polymers, whether or not cross-linking. Additional polymer layers mayoptionally be disposed over at least a portion of the donor polymer 23as well.

Insulative layers, including the donor polymer 23 and the receptorpolymer 22, may have any of a wide range of dimensions, individually orcollectively. For example, with respect to the collective thickness ofthe insulative layers, at least thick wall, thin wall, ultra thin wall,and ultra ultra thin wall wires 40 may be manufactured according to themethods disclosed herein. Exemplary thicknesses of collective insulativelayers may range From about 0.16 mm to about 1.28 mm. The thicknessratio of donor polymer 23 to receptor polymer 22 may vary. If thereceptor polymer 22 is more expensive, it may be advantageous to usejust enough receptor polymer 22 to satisfy technical specifications forthe particular wire 40 being manufactured. Exemplary thickness ratios(by volume) of receptor polymer 22 to donor polymer 23 may be about 1:1,about 1:1.5, about 1:2 or about 1:5. The low end of this range may havemore direct application to smaller gauge wires such as automotiveignition wires, and the high end of this range may have more directapplication to larger gauge wires, for example, battery wires. Dependingupon the technical specifications for resultant wire 40, thicknessratios may be lower or higher than the specific ranges exemplifiedherein.

Insulative layers, including the layers comprising donor polymer 23 andthe receptor polymer 22, may have a wide range of properties, includingelectrical properties, individually or collectively. For example, anaverage dielectric constant for the collective insulative layers madeusing the methods disclosed herein may be as lower as or lower thanabout 1.2, and the dielectric constant may be as high as or higher thanabout 7.

Insulative layers other than the layers comprising donor polymer 23 andthe receptor polymer 22 may comprise a broad range of materials. Forexample, it is contemplated that tapes, separators, foils, shields andbraids made from a broad cross-section of materials may be included asinsulative layers. Such insulative layers may reside between theconductive core 15 and the layer comprising receptor polymer 22, betweenthe receptor polymer 22 and the donor polymer 23, and/or outside thedonor polymer 23.

Manufacturing Methods

A wide range of manufacturing methods may be used to create amulti-layer wire pre-product 25 and ultimately resultant wire 40.Referring to FIG. 1, co-extrusion is shown as an exemplary manufacturingmethod to create a multi-layer wire pre-product 25 comprising aninsulative layer including a receptor polymer 22 and comprising aninsulative layer including a donor polymer 23. A conductive core 15 isfed into an extruder 20. Monomers, oligomers or polymers to form across-linkable receptor polymer 22 are added to a hopper of the extruder20. No curing agent is added. Separately, monomers, oligomers orpolymers to form a donor polymer 23 are added to a different hopper ofthe extruder 20. In this example, curing agent to be associated with thedonor polymer 23 is included in the hopper with the starting materialsto form the donor polymer 23 and any other starting materials. Areceptor polymer 22 is co-extruded with a donor polymer 23, the donorpolymer 23 being associated with a curing agent by being extruded withthe curing agent. A multi-layer wire pre-product 25 is generated fromthe co-extrusion process where a donor polymer 23 is disposed about thereceptor polymer 22, which is in turn disposed about the conductive core15.

Referring to FIG. 2, serial extrusion, also referred to as tandemextrusion, is shown as an exemplary manufacturing method to create amulti-layer wire pre-product 25. Two extruders are used, extruder 20 andextruder 21. Extruder 20 accepts a feed of conductive core 15, andaccepts starting materials into a hopper to extrude, at least, areceptor polymer 22 about the conductive core 15. No curing agent isadded. The product of extruder 20 is fed to extruder 21. In the exampleof FIG. 2, the starting materials to form donor polymer 23 are added tothe hopper with a curing agent to be associated with the donor polymer23 by being processed in the extruder 20 together with donor polymer 23.A multi-layer wire pre-product 25 is generated from the serial extrusionwhere a donor polymer 23 is disposed about the receptor polymer 22,which is in turn disposed about the conductive core 15.

Additional manufacturing methods are contemplated to generate themulti-layer wire pre-product 25. For example, a receptor polymer 22 maybe extruded about a conductive core 15 in a completely separate processfrom the extrusion of a donor polymer 23, and the layers are broughttogether manually or by other methods, including manual labor, prior toheat curing.

If a receptor polymer 22 is extruded in a separate process from theextrusion of the donor polymer 23, then the extrusion temperature forthe receptor polymer 22, substantially free of curing agent, is notlimited to those temperatures below a cure temperature for a particularcross-linkable polymer and curing agent combination. Extrusiontemperatures below the cure temperatures may still be used, but higherextrusion temperatures may be useful for, for example, increasingmanufacturing line speeds. By way of non-limiting example, extrusiontemperatures for a receptor polymer 22 can be as high or higher thanabout 125° C., about 200° C., or about 300° C.

If receptor polymer 22 and donor polymer 23 are co-extruded, times andtemperatures for extrusion should be set to minimize migration of curingagents from the donor polymer 23 to the receptor polymer 22 duringextrusion to avoid scorching. The temperature may depend upon thematerials selected for the donor polymer 23 and the receptor polymer 22.Typical extrusion temperatures are less than about 125° C., less thanabout 100° C., or less than about 80° C. The time of extrusion shouldmaximize line speed without sacrificing the desired properties inresultant wire 40 below technical specifications.

Depending upon the particular method of manufacturing multi-layer wirepre-product 25 selected, different extruders 20 may be selected. Singlehopper and dual hopper extruders may be used. New and used exemplaryextruders 20 are commercially available from many sources, including butnot limited to Davis Standard or Progressive Machinery, Inc.

Referring to FIGS. 1 and 2, after the multi-layer wire pre-product 25has been formed, it is heat cured at curing station 35, which maycomprise a steam cure station. As the multi-layer pre-product 25 is runthrough the heat curing station 35, the donor polymer 23 begins to melt.Then, curing agent in the donor polymer 23 migrates from the donorpolymer 23, through any intermittent layers, and into the receptorpolymer 22. The cross-linking reaction commences in, at least, thereceptor polymer 22. The cross-linking of any other cross-linkablepolymers also occurs during curing. Collectively, the insulative layersabout the conductive core 15 are the insulation of resultant wire 40.The state of cure of the insulation of resultant wire 40 will depend, inpart, on the time and temperature of cure.

Again, faster line speeds are generally more commercially desirable thanslower line speeds, so high cure temperatures and short cure times maybe used so long as the time and temperature for cure permit sufficientcross-linking so that insulation of the resultant wire 40 may satisfytechnical specifications. Typical cure times may range anywhere fromabout 20 seconds or 30 seconds to about 2 minutes to about 5 minutes toabout 10 minutes. Typical cure temperatures may be as low as about 130°C. or about 140° C., and may be as high as about 170° C., about 180° C.or about 200° C. The technical specifications for the resultant wire 40drive the cure times and the cure temperatures. Thus, it is contemplatedthat both cure times and cure temperatures may be higher or lower thanthe exemplary ranges disclosed herein.

A wide range of equipment and methods of heat curing may be used. Suchequipment may include Davis Standard steam tube cure equipment. It iscontemplated that the heat curing need not be applied heat from anexternal source. That is, the heat that initiates curing may begenerated from an exothermic reaction in the materials. Any commerciallyreasonable manufacturing line speed can be selected for use herein.Typical manufacturing line speeds may be from about 300 m/min to about1250 m/min Unexpectedly, when manufacturing line speeds were as high asabout 900 m/min or higher, and the degree of cross-linking in theinsulative layer including the receptor polymer 22 was less than 75%,the resultant wires 40 made by the methods disclosed herein wereexceptionally resistant to scrape abrasion and passed the tests setforth in ISO 6722 set forth above.

Example 1

Copper wire was fed to a Davis Standard extruder, and PETROTHENE® HDPEwas added to the hopper. The wire feed had a cross sectional area ofabout 0.5 mm². The HDPE was extruded at 200±5° C. for 120 minutes andcollected for use as a receptor polymer for wire samples to be prepared.A first sample of PETROTHENE® LDPE comprising 0.5 wt % of VULCUP R®curing agent was extruded for use as a low concentration donor polymer.A second sample of PETROTHENE® LDPE comprising 1.5 wt % of VULCUP R®curing agent was extruded for use as a high concentration donor polymer.The receptor polymer was inserted into the low concentration donorpolymer and cured at 200±5° C. for about 1.5 minutes. Three curedsamples were collected and tested for state of cure by ASTM D2765solvent extraction. In each instance, a state of cure of greater than50% was achieved. Additional receptor polymer samples were inserted intohigh concentration donor polymer cured at 200±5° C. for about 1.5 min.Three cured wire samples were collected and tested for state of cure byASTM D2765 solvent extraction. In each instance, a state of cure ofabout 70% was achieved. The results are graphically depicted in FIG. 5.

Example 2

A cured wire with a low concentration donor polymer produced in Example1 was tested for scrape abrasion. Similarly, a cured wire with a highconcentration donor polymer produced in Example 1 was tested for scrapeabrasion. The collective insulative layers of the cured wire made withthe low concentration donor polymer remained in tact following over 700cycles of abrasion scrapes with a needle having a diameter of 0.45±0.01mm. The collective insulative layers of the cured wire made with the lowconcentration donor polymer remained in tact following over 600 cyclesof abrasion scrapes with a needle having a diameter of 0.45±0.01 mm.Unexpectedly, both heat-cured samples exceeded a technical requirementthat the insulative layer or layers above a conductive core remain intact following at over 600 cycles of abrasion scrapes with a needlehaving a diameter of 0.45±0.01 mm. The results are graphically depictedin FIG. 6.

Example 3

Copper wire was fed to a Davis Standard extruder, and PETROTHENE® HDPEwas added to the hopper. The wire feed had a cross sectional area ofabout 0.35 mm². The HDPE was extruded at 200±5° C. for 60 minutes andcollected for use as a receptor polymer for wire samples to be prepared.BOREALIS® Polyethylene LDPE comprising 1.5 wt % of VULCUP R® curingagent was extruded for use as a low concentration donor polymer at 100°C. for 20 min. The extruded HDPE was inserted into the extruded LDPEprior to steam cure. Cure temperatures were set to 200±5° C. In onetrial, line speeds were set at about 98 m/min. In a second trial, linespeeds were set at about 457 m/min. In the first trial, the state ofcure was determined to be greater than 73%, and the scrape abrasionresistance was determined to be greater than 250 needle scrapes. In thesecond trial, the state of cure was determined to be greater than 60%,and the scrape abrasion resistance was determined to be greater than 250needle scrapes. Unexpectedly, across the range of line speeds, the curedwire exceed the technical requirements of an ability to withstand 200cycles of abrasion scrapes with a needle having a diameter of 0.45±0.01mm.

Example 4

Copper wire was fed to a Davis Standard extruder, and PETROTHENE® HDPEwas added to the hopper. The wire feed had a cross sectional area ofabout 0.5 mm². The HDPE was extruded at 200±5° C. for 60 minutes andcollected for use as a receptor polymer for wire samples to be prepared.BOREALIS® Polyethylene LDPE comprising 1.5 wt % of VULCUP R® curingagent was extruded for use as a low concentration donor polymer at100±5° C. for 20 minutes. The extruded HDPE was inserted into theextruded LDPE prior to steam cure. Cure temperatures were set to 200±5°C. In one trial, line speeds were set at about 98 m/min. In a secondtrial, line speeds were set at about 457 m/min. In the first trial, thestate of cure was determined to be greater than 65%, and the scrapeabrasion resistance was determined to be greater than 700 needlescrapes. In the second trial, the state of cure was determined to begreater than 53%, and the scrape abrasion resistance was determined tobe greater than 700 needle scrapes. Unexpectedly, across the range ofline speeds, the cured wire exceed the technical requirements of anability to withstand 300 cycles of abrasion scrapes with a needle havinga diameter of 0.45±0.01 mm.

Example 5

Copper wire was fed to a Davis Standard extruder, and PETROTHENE® HDPEwas added to the hopper. The wire feed had a cross sectional area ofabout 1.0 mm². The HDPE was extruded at 200±5° C. for 60 minutes andcollected for use as a receptor polymer for wire samples to be prepared.BOREALIS® Polyethylene LDPE comprising 1.5 wt % of VULCUP R® curingagent was extruded for use as a low concentration donor polymer at100±5° C. for 20 minutes. The extruded HDPE was inserted into theextruded LDPE prior to steam cure. Cure temperatures were set to 200±5°C. In one trial, line speeds were set at about 98 m/min. In a secondtrial, line speeds were set at about 457 m/min. In the first trial, thestate of cure was determined to be greater than 64%, and the scrapeabrasion resistance was determined to be greater than 800 needlescrapes. In the second trial, the state of cure was determined to begreater than 62%, and the scrape abrasion resistance was determined tobe greater than 800 needle scrapes. Unexpectedly, across the range ofline speeds, the cured wire exceed the technical requirements of anability to withstand 500 cycles of abrasion scrapes with a needle havinga diameter of 0.45±0.01 mm.

Example 6

Copper wire was fed to a Davis Standard extruder, and PETROTHENE® HDPEwas added to the hopper. The wire feed had a cross sectional area ofabout 1.5 mm². The HDPE was extruded at 200±5° C. for 60 minutes andcollected for use as a receptor polymer for wire samples to be prepared.BOREALIS® Polyethylene LDPE comprising 1.5 wt % of VULCUP R® curingagent was extruded for use as a low concentration donor polymer at100±5° C. for 20 minutes. The extruded HDPE was inserted into theextruded LDPE prior to steam cure. Cure temperatures were set to 200±5°C. In one trial, line speeds were set at about 98 m/min. In a secondtrial, line speeds were set at about 457 m/min. In the first trial, thestate of cure was determined to be greater than 66%, and the scrapeabrasion resistance was determined to be greater than 3000 needlescrapes. In the second trial, the state of cure was determined to begreater than 60%, and the scrape abrasion resistance was determined tobe greater than 3000 needles scrapes. Unexpectedly, across the range ofline speeds, the cured wire exceed the technical requirements of anability to withstand 1500 cycles of abrasion scrapes with a needlehaving a diameter of 0.45±0.01 mm.

Example 7

Copper wire was fed to a Davis Standard extruder. The wire feed had across sectional area of about 1.5 mm². PETROTHENE® HDPE was added to thehopper and was extruded at 200° C. for 60 minutes then collected for useas a receptor polymer. BOREALIS® Polyethylene LDPE containing 1.5% byweight of VULCUP R® curing agent was extruded at 100±5° C. for 20minutes and collected for use as a low concentration donor polymer. Theextruded HDPE was inserted into the extruded LDPE prior to steam cure.Cure temperatures were set to 200±5° C. Each of the samples was testedor scrape abrasion with a needle having a diameter of 0.45±0.01 mm. Thetests were run at 38° C., 43° C., 49° C. and 54° C. Unexpectedly, thecollective insulative layers comprising both the donor and the receptorpolymer remained in tact after more than 3400 scrapes. Alsounexpectedly, the performance remained substantially constant over thetested temperature range. The results are graphically depicted in FIG.7.

With regard to the processes, systems, methods, heuristics, etc.described herein, it should be understood that, although the steps ofsuch processes, etc. have been described as occurring according to acertain ordered sequence, such processes could be practiced with thedescribed steps performed in an order other than the order describedherein. It further should be understood that certain steps could beperformed simultaneously, that other steps could be added, or thatcertain steps described herein could be omitted. In other words, thedescriptions of processes herein are provided for the purpose ofillustrating certain embodiments, and should in no way be construed soas to limit the claimed invention.

Accordingly, it is to be understood that the above description isintended to be illustrative and not restrictive. Many embodiments andapplications other than the examples provided would be upon reading theabove description. The scope of the invention should be determined, notwith reference to the above description, but should instead bedetermined with reference to the appended claims, along with the fullscope of equivalents to which such claims are entitled. It isanticipated and intended that future developments will occur in the artsdiscussed herein, and that the disclosed systems and methods will beincorporated into such future embodiments. In sum, it should beunderstood that the invention is capable of modification and variationand is limited only by the following claims.

All terms used in the claims are intended to be given their broadestreasonable constructions and their ordinary meanings as understood bythose skilled in the art unless an explicit indication to the contraryin made herein. In particular, use of the singular articles such as “a,”“the,” “said,” etc. should be read to recite one or more of theindicated elements unless a claim recites an explicit limitation to thecontrary.

What is claimed is:
 1. A method of manufacturing a wire, comprising:extruding a cross-linkable receptor polymer, substantially free ofcuring agent, about a conductive core; extruding a donor polymer,wherein the donor polymer comprises a curing agent; disposing theextruded donor polymer about the receptor polymer, thereby forming amulti-layer wire pre-product, wherein the donor polymer has a melttemperature lower than a melt temperature of the receptor polymer; andheat curing the multi-layer wire pre-product, wherein heat curingcomprises: subjecting the multi-layer pre-product to a heat curingstation operating at a cure temperature from about 130° C. to about 200°C.; and melting the donor polymer, such that the curing agent in thedonor polymer migrates from the donor polymer to the receptor polymer;wherein the thickness of the receptor polymer to the thickness of thedonor polymer is about 1:1 to about 1:5.
 2. The method of claim 1,wherein extruding the receptor polymer comprises disposing the receptorpolymer in direct contact with the conductive core.
 3. The method ofclaim 1, wherein the conductive core comprises a semi-conductivematerial.
 4. The method of claim 1, wherein the conductive corecomprises at least one of solid or stranded copper, nickel silver,beryllium, phosphor bronze, nickel, copper-clad aluminum, copper-cladsteel, aluminium and steel.
 5. The method of claim 1, wherein the donorpolymer has a melt temperature lower than a melt temperature of thereceptor polymer by at least about 5° C.
 6. The method of claim 1,wherein disposing the donor polymer about the receptor polymer comprisesco-extruding the receptor polymer and the donor polymer.
 7. The methodof claim 1, wherein disposing the donor polymer about the receptorpolymer comprises serially extruding the receptor polymer and the donorpolymer.
 8. The method of claim 1, wherein disposing the donor polymerabout the receptor polymer comprises placing the donor polymer in directcontact with the receptor polymer.
 9. The method of claim 1, wherein theconductive core has a cross-sectional area of at least about 1.5 mm² andwherein heat curing comprises subjecting the multi-layer wirepre-product to a heightened temperature for time sufficient to form awire including insulation capable of remaining intact following at least1500 cycles of abrasion scrapes with a needle having a diameter of about0.45±0.01 mm.
 10. The method of claim 1, wherein the conductive core hasa cross-sectional area of not greater than 0.22 mm² and wherein heatcuring comprises subjecting the multi-layer wire pre-product to aheightened temperature for time sufficient to form a wire includinginsulation capable of remaining intact following at least 150 cycles ofabrasion scrapes with a needle having a diameter of about 0.45±0.01 mm.11. The method of claim 10, wherein the time sufficient is at leastabout 20 seconds.
 12. The method of claim 1, wherein the conductive corehas a cross-sectional area of no more than about 0.22 mm² and whereinheat curing comprises subjecting the multi-layer wire pre-product to aheightened temperature for time sufficient to form a wire includinginsulation capable of remaining intact following an abrasion scrape witha 150 J garnet sandpaper having a length of about 200 mm that is exertedwith an applied force of at least about 0.63 N.